This invention relates to an improved, accommodative, intraocular lens system operable to be positioned within the interior of an evacuated capsular bag of a human eye. More specifically, this invention relates to an open accommodative, intraocular lens system method and apparatus operable to be inserted within an evacuated capsular bag of a human eye following extracapsular surgery to remove and replace a dysfunctional natural crystalline lens. The invention finds particular application in restoring multi-focal vision following cataract surgery, correction of myopia, correction of presbyopia and treatment of the symptoms of retinal damage, such as, age related macular degeneration of the human eye.
In the human eye, multi-focal vision is provided by a combination of a convex-concave lens, known as the cornea, positioned in front of the iris and a bi-convex lens positioned within a clear elliptical envelope behind the iris and in front of the vitreous humor of the eye. Accommodation of vision at both infinity and near vision of 250 mm is provided by a peripheral muscular body extending about the capsular bag and connected to the equator thereof by Zonula of Zinn which are thin strands attaching the equator of the capsular bag to the ciliary muscles of a human eye system. Tension and the relaxation of the ciliary muscles causes the capsular bag to lengthen or contract which varies the focus of the eye.
In certain instances at an early age, such as trauma or heredity, or in later stages of the life cycle, the natural crystalline lens of a human becomes cloudy and hardened, somewhat like milk glass, which occludes vision and results in eventual blindness. This condition is known as a cataract and was a major source of blindness in mankind for centuries. As early as 1766 Cassanova, in his memoirs, suggested that an intraocular lens could be implanted within a human eye to replace an opaque natural crystalline lens. It was not until 1949, however, that a Dr. Harold Ridley, at the Thomas Hospital in London, inserted the first intraocular lens within the eye of a woman of about 60 years of age following cataract extraction. Early IOLs, however, tended to dislocate, cause iris atrophy and in some instances secondary glaucoma. Attempts to overcome the early disadvantages of Dr. Ridley""s solid posterior chamber lens included placement of a lens in the anterior chamber, in front of the iris. In addition Dr. Binkhorst of Holland invented an iris clip lens and Dr. Choyce an iris plane lens. However, both anterior chamber and iris fixed lenses created a risk of damages to delicate iris tissue.
An advanced in the intraocular lens art occurred when Dr. Shearing invented the first, practical, posterior chamber lens. Dr. Shearing""s design included a bi-convex polymethylmethacrylate (PMMA) lens body which was positioned behind the iris and against the ciliary muscle or within the capsular bag. The Shearing IOL was maintained in a generally central axis of vision by thin strand haptics that extended radially from the peripheral edge of the lens optic and were curved at their distal ends. The curved portions of the haptics abutted against peripheral tissue of the eye to support the lens. Although the Shearing lens haptics had small arc contact zones, the success of the lens led other pioneers to develop a variety of haptic designs, such as, a C-loop or an S-loop and other designs to relieve trauma to adjacent contact tissue. A significant limitation of all fixed focus intraocular lens designs is that the focal point is fixed at infinity. Accordingly, for all near vision tasks, conventional reading glasses became necessary. In this connection, it is believed that several million pairs of reading glasses are sold annually within the United States alone.
In addition to the incidences of cataract formation and its attendant tendency to blindness, reductions in both amplitude and speed of accommodation with age are well known. This condition is known as presbyopia. The amplitude of accommodation decreases progressively with age from some 14 diopters in a child of ten years to near zero at age fifty or so. The exact explanation for the physiological phenomena is not well documented, however, it is observed that the curvatures of excised senile lenses were considerably less than those of juvenile ones. This failure could be due to a hardening of the lens material, sclerosis, decrease in modulus of elasticity, or to a decrease in thickness of the capsule or a combination of the above. Regardless of the cause, it is a recognized fact that beginning at about age 40-45 correction for both near and far vision becomes necessary in most humans. Conventional techniques include bifocal glasses, bifocal contact lenses, contact lenses for distance and reading glasses for near vision, and mono-focus contact lens sets where one eye carries a contact lens for distance vision and the other eye carries a contact lens for reading. Still further refractive surgery for distance vision coupled with reading glasses has been used successfully to correct presbyopia. Notwithstanding the grateful relief of being able to see clearly at both near and distance, all of the above solutions are compromises, in one form or another, and are dramatically more inconvenient than the natural bifocal vision of youth.
A somewhat related visual dysfunction in youth and young adults is mild to severe myopia or the loss of an ability to clearly focus at distance. Glasses, contact lenses or refractive surgery are the most common forms of accommodation, however, with certain cases of myopia it may be necessary to correct vision up to 30 to 40 diopters. As the degree of myopia increases the use of conventional solutions becomes less attractive and it would be highly desirable to be able to reliably correct this patient concern.
Still further, as humans age, or through viral inflammations or trauma, deterioration in retinal cells, including macular degeneration, can cause a dramatic loss of perception of light and color by rods and cones of the retina. In certain instances a degree of relief for humans suffering from impairment of vision from the loss of retinal cells can be achieved by increasing the intensity or magnification of images presented to healthy cells. In certain instances of macular degeneration it would be desirable to present a patient with an option of a correction of 30 to 70 diopters. This magnitude of correction is not readily achievable with presently known techniques.
The limitations to vision outlined in the proceeding are not intended to be exhaustive but are major concerns and represent limitations placed on mankind of impaired vision occasioned from trauma, disease, and/or age. It would be highly desirable if these limitations could be addressed and minimized or eliminated and thus restore to patients at least a portion of the accommodation and clarity of the vision of their youth.
It is a general object of the invention to provide a method and apparatus to obviate or minimize limitations to accommodated bifocal vision of the type previously described.
It is another object of the invention to provide an intraocular lens system which is operable to restore a patient""s multi-focal vision following extracapsular cataract extraction.
It is a further object of the invention to provide an intraocular lens system which can be used as a replacement of a patient""s natural crystalline lens to accommodate and offset presbyopia limited vision with age.
It is a related object of the invention to provide an intraocular lens system that can be used in place of a patient""s natural crystalline lens to correct instances of mild to severe myopia.
It is yet another object of the invention to provide an intraocular lens system which can be used to improve vision in patients having retinal deterioration, such as, macular degeneration.
It is a specific object of the invention to provide an intraocular lens system that is operable to utilize the natural physiology of the human eye to restore accommodative multi-focal vision to a patient.
It is yet another object of the invention to restore a patient""s vision following cataract surgery or for correction of presbyopia without using refractive surgery, contact lenses, or glasses as a part of the corrective solution.
It is still another object of the invention to provide an intraocular lens system solution to create a vision augmentation of 70 to 90 diopters without use of thick glasses or radical refractive surgery
In at least one preferred embodiment of the invention, intended to accomplish the above, and other, objects of the invention are achieved by an open chamber, accommodative, intraocular lens system operable to be positioned within the interior of an evacuated capsular bag of a human eye. The inventive intraocular lens system includes a first anterior lens optic and a second posterior lens optic which are arranged in axial alignment visually. An open chamber, haptic system is connected between the two lenses and in a preferred form three haptics segments are fashioned in the form of elliptical segments which are connected at their ends to the peripheral rims of the lens bodies and arc outwardly away from the visual axis of the lenses.
The overall cross-sectional shape of the inventive intraocular lens system is elliptical and is designed to fit smoothly within the interior of a patient""s capsular bag. The elliptical haptic elements are flexible and as the capsular bag is peripherally pulled outwardly at its equator the bag contracts. This contraction is produced by a patient""s natural vision accommodations by the ciliary muscles of the eye. In this, the anterior lens is moved axially toward the posterior lens to provide vision at infinity. As the ciliary muscles are constricted and move radially inward, for near vision accommodation, tension on connective zonula decreases and the patient""s capsular bag thickens allowing the haptics to assume their natural memory state.
Although the use of a two optic lens system is preferred, wherein the anterior lens is bi-convex and the posterior lens is concavo-convex to provide a corrective range of accommodation of about 4 diopters following extracapsular cataract surgery, other lens embodiments are contemplated by the subject invention. In this, other lens cross-sectional configurations can be used, for example, concavo-planar or concavo-convex for either the anterior or posterior. lens. In still other instances it may be desirable to remove the posterior lens entirely or eliminate its optic function by using a biplanar lens body. Finally, the invention also envisions adding more than two lenses, such as three lenses, in instances where extreme dioptive correction is desirable.
In a preferred embodiment three elliptical haptic segments are use extending at an arc of about 40 degrees outwardly from the rims of the lens optics and are peripherally spaced around the periphery with 80 degree segments of open space. These haptic segments are elliptical in cross-section takes along a line of sight of the lens system and are fashioned in a natural state to have an elliptical ratio of 0.96. Other arrangements of the haptics are also envisioned such as two wider based haptics or four or more haptics that would be thinner in outer width. The underlying criteria is that the haptics are flexible enough to enable relatively unrestricted accommodation movement of the anterior lens toward the posterior chamber lens of about 1.9 mm or so in response to the natural movement of the ciliary muscle and zonula attached to the capsular bag while simultaneously being stiff enough to support a lens or lenses of the optic system in visual axial alignment within the capsular bag of a patient""s eye.